Trump did not expound on his unfounded accusations about 30-year-old Jon Ossoff, but the president's Twitter broadside a day before the special primary underscores how big a Democratic victory would be nationwide and in Atlanta's historically conservative northern suburbs.
Ossoff, who has used anti-Trump sentiments nationally to collect at least $8.3 million in campaign contributions, countered Monday that Trump is "misinformed," but added that he's "glad the president is interested in the race."
Republicans and Democrats alike see the contest as an important barometer of Trump's standing ahead of 2018 midterm elections, when Democrats will try to regain control of Congress.
The Georgia district, represented previously by Trump's new health secretary, Tom Price, encompasses reliably Republican territory across parts of three metro Atlanta counties. But Trump underperformed here in November, barely edging Democrat Hillary Clinton and falling short of a majority. In 2012, by contrast, Republican nominee Mitt Romney garnered more than 60 percent of the vote.
Even the leading Republican candidates concede that Ossoff will lead an 18-candidate "jungle primary" that places all candidates on the same ballot. The question is whether he can win an outright majority.
GOP hopeful Karen Handel said Monday that she is confident enough Republicans will cast ballots to hold Ossoff short of a majority, thus setting up a June 20 runoff between the Democratic upstart and Tuesday's top Republican performer.
"Republican voters are not going to sit by and let this district go to a Democrat," Handel said.
But the mere possibility has national observers watching closely, particularly because the district is dominated by the kind of suburban voters Democrats need to have any chance at a House majority.
The scrutiny grew even more intense after last week's special congressional election in Kansas, where Republican Ron Estes won by just single-digits in a Wichita-based district that Trump had carried easily.
Ossoff on Monday continued walking a fine line between embracing the national energy and trying to make the contest a purely local one. "This is not about me. This is about us," he told a few hundred supporters Monday night. "This is about this community. This is about the kind of community we want to live in. The kind of country we believe in."
Ossoff did not mention his exchange with Trump - or call the president by name at all - during his remarks.
Handel, a GOP establishment favorite who served previously as Georgia secretary of state, also has worked to localize the race.
"My closing argument is the same as my opening argument, that we need an experienced individual with a track record of delivering real results," she said while campaigning Monday in an upscale shopping district.
That has made her an outlier among top Republican contenders.
Wealthy technology executive Bob Gray has cozied up to Trump from the start, running ads that show him, literally, draining a swamp - a nod to one of Trump's campaign signatures. Gray pledges to be a "willing partner" for the new administration.
Former state Sen. Judson Hill is touting his endorsement from Florida Sen. Marco Rubio, one of a gaggle of Republican presidential hopefuls that Trump vanquished. Hill's campaign is using Rubio on a recorded phone pitch to Republican households.
Ossoff, meanwhile, has tried to capitalize on intense anti-Trump sentiments among liberals, while still coaxing disaffected independents and moderate Republicans who normally wouldn't consider voting Democratic.
Responding to Trump's tweet, Ossoff said in his statement that he is "focused on bringing fresh leadership, accountability and bipartisan problem solving to Washington."
National Republicans have sought to blunt Ossoff's momentum by tying him to national Democrats, particularly House Minority Leader Nancy Pelosi. The California Democrat is an unpopular figure in this Georgia district that once sent former House Speaker Newt Gingrich to Capitol Hill.
Still, that message hasn't come with the same financial muscle as Ossoff's non-stop television campaign. The Congressional Leadership Fund, a political action committee backed by House Speaker Paul Ryan, has plunked more than $2 million into Ossoff attacks, an impressive sum but only about a quarter of the Democrat's campaign haul.
Ossoff's quest for an outright victory may depend on low Republican turnout.
Almost 55,000 voters cast early ballots, according to the Georgia Secretary of State. Various campaigns say they expect somewhere between 100,000 and 125,000 total votes out of nearly 440,000 registered active voters. The lower the turnout, the greater the chance that Ossoff's enthusiastic core of support would clear the majority threshold.
Follow Barrow on Twitter at https://twitter.com/BillBarrowAP .
Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.